The Hamster Harderian Gland: Regulation of Morphology and Porphyrin Biosynthesis by Gonadal Steroids

Spike, Rosemary Catherine (1986) The Hamster Harderian Gland: Regulation of Morphology and Porphyrin Biosynthesis by Gonadal Steroids. PhD thesis, University of Glasgow.

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The Harderian gland is an orbital structure found in most classes of terrestrial vertebrates. The gland is particularly well developed in rodents, where in addition to the normal mammalian lipid secretion, porphyrins (precursors of haem) are also produced and stored, normally as solid intraluminal deposits. In this thesis, the golden hamster has been used exclusively since the female hamster Harderian gland is possibly the richest source of mammalian porphyrins known, while the male gland contains very little porphyrin. Sex differences are also found in the activities of five of the enzymes in the biosynthetic pathway, with levels being greater in the female. A number of morphological sexual dichotomies also exist; briefly, the female gland has only one epithelial cell type (Type I), while the male gland has two cell types (Type I and Type II). Both male cell types contain unique ultrastruetural features, the polytubular complexes, which are not found in the normal female gland. The female gland has approximately 40x more interstitial and capsular mast cells than the male gland. Gonadal hormones are responsible for these dichotomies since castration of males results in loss of Type II cells and polytubular complexes, the appearance of large intraluminal porphyrin accretions, a rise in porphyrin content and enzyme activity and an increase in mast cells. Androgen administration to females results in virilization of the gland. The aims of this thesis were: 1 . To investigate the control of porphyrin biosynthesis within the Harderian gland by exogenous and endogenous steroid manipulation, primarily in the female hamster. 2. To investigate the relationship between porphyrin biosynthesis in the Harderian gland and the rest of the body. 3. As a prerequisite to the histological investigations of 1, to investigate the effects of various fixatives in preserving the different forms of porphyrin deposits within the gland. Porphyrin is normally deposited as solid intraluminal accretions in the female gland, but ovariectomised and post-reproductive senescent females also exhibit interstitial porphyrin deposits, either surrounded by macrophages forming foreign body giant cells or within individual macrophages. For quantitative evaluation of changes resulting from hormone manipulations it is therefore important to use a fixative which preserves these various forms of porphyrins, which are soluble in a wide range of solvents. Four commonly used fixatives were used and porphyrin loss was assessed spectrofluorimetrieally in each fixative, the subsequent dehydration and clearing steps in each routine, and the residue left at the end of the processing. These accumulated values were compared with a similar amount of tissue from the same animals placed directly into methanol. Good approximations were obtained. The results indicated that both Bouin's fixative and Acid/formal/alcohol resulted in unacceptably high losses of porphyrin since neither of these fixatives fix lipids to which porphyrins are thought to be complexed. While Dichromate fixation resulted in less than 2% porphyrin loss it produced tissue which was difficult to section. Both glutaraldehyde routines produced approximately 8% porphyrin loss hut the use of amyl acetate as the clearing agent, rather than chloroform, produced better results in terms of tissue preservation especially if the tissue was to he re-embedded for T. E. M. or S. E. M. Quantitative assessments of the effects of ovariectomy on the morphology, porphyrin content and porphyrin synthesising enzyme activity of the Harderian gland of the female hamster confirms the link between gonadal hormones and gland structure and activity. The results indicate that ovarian hormones are necessary to maintain the morphology and activity of the normal female Harderian gland since ovariectomy results in a series of degenerative changes in gland morphology, and a decrease in enzyme activity. Furthermore, a study investigating the time course of change following ovariectomy demonstrates that this is a progressive phenomenon. Similar, albeit less marked, changes occur in post-reproductive senescent females. Pregnancy and lactation also affected porphyrin biosynthesis in multiparous hamsters, again suggesting a link between gland activity and circulating ovarian hormones. Androgen administration to ovariectomised females resulted in morphological virilization of gland features and a significant decrease in porphyrin content, while enzyme levels fell to normal male values. Castration of male hamsters produced an increase in porphyrin content and enzyme activity which was modified by oestrogen or progesterone administration but inhibited by testosterone. Circulating levels of testosterone maintain the male gland characteristics even in senescent animals. (Abstract shortened by ProQuest.).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Morphology
Date of Award: 1986
Depositing User: Enlighten Team
Unique ID: glathesis:1986-77397
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jan 2020 09:09
Last Modified: 14 Jan 2020 09:09

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